each certificate of the list is verified against the next certificate, until
it can be verified against a system certificate (system certificates are assumed as trusted)

This helper only check that the chain of certificate is valid, which means that each items
received are signed by the next one, or by a system certificate. Some extra checks need to
be done at the user level so that the certificate chain received make sense in the context.

for example for HTTP, the user should typically verify the certificate subject match the URL
of connection.